WPf cropping image help

Hello,

I recently got a project and I need help how to crop an image, i got all the way where you get the image from browsing to your local disk, and it comes up on the image viewer, but now I need help on this part,  I want the user to click on the button to start cropping it, after the user has made a rectangle around the part of the image he wants to crop, click on the button below the start cropping where i guess the button can say "crop it", or just change the start cropping and it turns into "crop it" which i think would be nice. But anyways, after the user clicks on the "crop it" it is now displayed on the imageviewer. How can this be done? hopefully I explained myself clearly, again, just need help on how to do a basic crop image, i looked at a couple of examples:

http://www.codeproject.com/KB/WPF/ImageCropper.aspx#HowItWorks

and

http://www.codeproject.com/KB/WPF/CropAdorner.aspx

but they are no help, they say in there examples its easier... YA right!!! there code doesnt look easy, can anyone give me an easier example and explain in jr. programming terms : )

also I guess a good example about the croping would be like windows paint, how the user presses the button to start cropping then they can save it. etc.

Thank you